Field of the Invention
The invention relates to a diaphragm adjusting arrangement in a photographic enlarging or copying apparatus having several lenses with an adjustable diaphragm
2. Description of the Prior Art
Known photographic enlarging apparatuses are designed such that they can be used for producing photographic copies in different formats and from originals to be copied which are also available in different formats In order to obtain the large number of existing formats or the enlarging range required for this purpose, enlarging apparatuses of that type are equipped with several lenses of different focal distances which selectively can be moved into the working position. As a rule, each lens is also provided with an adjustable diaphragm in order to adapt the intensity of the copying light to the specific circumstances of the exposure to be carried out.
In German Patent DE-C 30 45 157, a lens carriage having three lenses is described, in which the diaphragms of the individual lenses, by means of a common adjusting device, can be adjusted manually to given positions which each correspond to a fixed diaphragm number, and the adjusted positions are detected by means of correspondingly arranged microswitches which are electrically connected with one another and with an indicating device. This type of a device is suitable for the adjusting and detecting of only a limited number of diaphragm numbers. It is also unsuitable for inclusion into an automatic control system, as it exists in modern enlarging apparatuses in connection with the exposure control and other measuring and control functions.
The manual adjustment of the lens diaphragms represents a limitation of the automatic operation of the enlarging apparatus with a corresponding prolongation of the processing times, and, in addition, represents a source of errors because of the danger that the diaphragm number on which the determination of the exposure is based does not correspond to the actually adjusted diaphragm number. In fact, without any direct communication between the diaphragm adjustment and the control functions of the enlarging apparatus, it is left to the operator to adjust the diaphragm number on which the determination of the exposure is based or to apply the adjusted diaphragm number correctly to the exposure control.